1. Field of Art
This invention generally relates to eyepieces used to project an image from a small display into the eye, for example as may be used with head or helmet mounted night vision systems.
2. Description of the Related Art
In certain applications, a small display in close proximity to a user's eye produces an image and an eyepiece projects that image into the user's eye. In this way, the user sees the image produced by the display. The image may be real, enhanced or virtual. It may replace, augment or overlay what the user would normally see. For example, in a virtual reality system, the user's natural surroundings may be blocked out and replaced entirely by images of a virtual world projected from the display system. A user might be sitting in his living room with rainy weather outside, but the display system projects images of a sunny beach instead. In an augmented or enhanced reality system, additional images may be added to the user's natural surroundings. For example, the user might be sitting in his office facing a blank wall, and the display system projects images so that it appears as if a computer screen is located on the wall. As another example, a pilot might be flying at night, and the display system projects night vision images or thermal infrared images over the otherwise dark outside. The display system may also project other information, such as the aircraft's heading, speed, attitude, etc.
Whatever the application, the display and eyepiece preferably are small, lightweight and low cost. However, wider field of view and higher resolution are also desirable. These requirements are inherently in conflict. Wider field of view and higher resolution typically means that the display and/or eyepiece will be larger, heavier and/or more costly. Currently available displays that meet typical requirements regarding size, weight and cost, often leave room for improvement with respect to field of view and/or resolution.
Thus, there is a need for approaches that can improve on currently available systems.